Figure 3-4. - Gas tungsten arc welding (GTAW).

(GTAW) (fig. 3-4) and gas metal arc welding (GMAW) (fig. 3-5). You will also hear these called "TIG" and "MIG." Gas shielded arc welding is extremely useful because it can be used to weld all types of ferrous and nonferrous metals of all thicknesses.

Now that we have discussed a few of the welding processes available, which one should you choose? There are no hard-and-fast rules. In general, the controlling factors are the types of metal you are joining, cost involved, nature of the products you are fabricating, and the techniques you use to fabricate them. Because of its flexibility and mobility, gas welding is widely used for maintenance and repair work in the field. On the other hand, you should probably choose gas shielded metal arc welding to repair a critical piece of equipment made from aluminum or stainless steel.

No matter what welding process you use, there is some basic information you need to know. The remainder of this chapter is devoted to this type of information. Study this information carefully because it allows you to follow welding instructions, read welding symbols, and weld various types of joints using the proper welding techniques.

Figure 3-5. - Gas metal arc welding (GMAW).

WELDING TERMINOLOGY

To become a skilled welder, you first need to learn the technical vocabulary '(language) of welding. The sections in this chapter introduce you to some of the basic terms of the welding language. Once you understand the language of welding, you will be prepared to interpret and communicate welding information accurately.

FILLER METALS

When welding two pieces of metal together, you often have to leave a space between the joint. The material that you add to fill this space during the welding process is known as the filler metal, or material. Two types of filler metals commonly used in welding are welding rods and welding electrodes.

The term welding rod refers to a form of filler metal that does not conduct an electric current during the welding process. The only purpose of a welding rod is to supply filler metal to the joint. This type of filler metal is often used for gas welding.

In electric-arc welding, the term electrode refers to the component that conducts the current from the electrode holder to the metal being welded. Electrodes are